A current CDMA standard, IS-2000-2, “Physical Layer Standard for cdma2000 Spread Spectrum Systems”, release 0, July 1999, allows the base station to disable a forward link channel transmission on a frame-by-frame basis. This is referred to herein as discontinuous transmission (DTX). However, information as to whether a particular frame was transmitted or was not transmitted is not known to the Mobile Station. In IS-2000-2 the following channels can be discontinuous: the Forward Dedicated Control Channel (F-DCCH), the Forward Supplemental Channel 1 (F-SCH1), and the Forward Supplemental Channel 2 (F-SCH2).
Several algorithms executed by the mobile station require information as to whether a frame was actually transmitted. In the context of this patent application this will be referred to as a “DTX detection” problem. Three examples that illustrate the DTX detection problem follow.
In a first example, when the forward link power control is enabled on the F-DCCH or the F-SCHn (n=1,2), the outer power control loop updates the current setpoint (operating point) based on the frame error information (CRC). However, if the frame was not transmitted the mobile station should not update the current setpoint. In order to accomplish this the mobile station needs to be able to detect whether actual frame transmission took place.
In a second example, the IS2000 Release A standard (IS-2000-2, “Physical Layer Standard for cdma2000 Spread Spectrum Systems”, release A, Jun. 9, 2000) specifies a forward link power control mode on F-DCCH (QIB (Quality Indicator Bit) power control). This procedure requires the detection of the F-DCCH frame transmission (DTX detection).
The IS2000 Release A standard also allows the power control subchannel on the forward link to be transmitted on the F-FCH or the F-DCCH, based on a parameter FPC_PRI_CHAN. When the power control subchannel is transmitted on the F-DCCH, the mobile station supervision procedures require DTX detection.
Prior to this invention, a satisfactory technique for solving the DTX detection problem was not available.